The PS3, impressively, uses barely anything when off; the Watt display on the Kill-A-Watt metering device showing between 0 and 1 watts.
When sitting idle at the crossbar navigation system, the equivalent to the Xbox 360 dashboard or the Wii's home menu, the PS3 used anywhere from 185 to 205 watts. When doing similar work the Xbox 360 uses 145 watts and the Wii just 15-20.
Now, for the gaming. We tested with three games and found consumption to be lowest when playing Tiger Woods 07, registering at 185-190 watts, and highest when playing Formula One Championship Edition, which demanded a rather more disconcerting 217 watts on average. By comparison the Xbox 360 comes in at 165 watts during gameplay with the Wii using only around 120. Finally, during Blu-ray playback the PS3 continued to draw a surprising 205 watts, just to spew the rather craptacular Ricky Bobby to my HDTV.